The conservative Club for Growth is putting out a new ad looking to boost Sen. Mike Lee, R-Utah, as he faces a tougher-than-anticipated challenge from independent Evan McMullin.

The video, backed by an $800,000 reservation, will begin airing statewide Wednesday through Election Day. The 30-second clip features former Gov. Jon Huntsman, who served one term and was later the U.S. ambassador to Russia during the Trump administration.

"There's a lot of noise out there right now, so let me tell you what I know about Mike Lee. I've worked with Mike since I was governor, and I know his heart. He has the unshakeable integrity that's all too scarce in politics. You might not always agree with Mike. I don't. But we can all agree that principled leadership and fidelity to the Constitution are paramount in difficult times. Let's send Mike Lee back to the Senate," Huntsman says in the ad.

The late buy suggests 11th-hour handwringing by some of Lee's allies over McMullin's bid.

Lee recently went on Fox News to plead with Sen. Mitt Romney, R-Utah, for his endorsement, and the FiveThirtyEight polling average only has Lee up by about 8 points after he won reelection in 2016 by more than 40.

McMullin has centered his challenge around Lee's communications discussing methods to challenge the 2020 election results after the race was over, accusing Lee of shedding his label as a "constitutional conservative." Lee notes he did not ultimately reject to certifying the Electoral College results.

He and his allies have accused McMullin -- who previously worked as a Republican congressional aide and then ran for president in 2016 as an independent -- of now being a closet Democrat, noting that the state Democratic Party endorsed him and did not run a candidate of its own. McMullin, though, has said he wouldn't caucus with either party in the Senate.

-- ABC News' Tal Axelrod

The newest John Fetterman ads feature words of support from former President Barack Obama, the latest high-profile surrogate to involve himself in Pennsylvania's crucial Senate race.

In the two spots – one a ad, the other on Obama60AfAm-Radio-Ad.mp3&data=05%7C01%7CIsabella.Murray%40abc.com%7C7277efb2875a46c461f508dab3a03634%7C56b731a8a2ac4c32bf6b616810e913c6%7C1%7C0%7C638019797957968210%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=um8ekH93S8edmAV1yI8%2BACuSGiPZ%2F%2FWN61EVdSf6mFQ%3D&reserved=0|radio> – Obama cites abortion rights, the protection of democracy and Fetterman's record on crime in trying to persuade voters to support the Democratic candidate.

"When the fate of our democracy and a women's right to choose are on the line, I know John will fight for Pennsylvanians," he says in both ads.

Notably, in the radio ad, Obama touts Fetterman's service on the state Board of Pardons, which opponent Dr. Mehmet Oz attacks repeatedly by accusing Fetterman of endangering Pennsylvanians by voting to commute the sentences of some convicted murderers.

"As Lieutenant Governor, John chairs the Board of Pardons and has helped people who were wrongfully convicted," Obama says.

In a statement, Fetterman said, "I am deeply grateful for President Obama's support in this race. I was proud to be one of the only elected officials in western Pennsylvania to endorse President Obama in the 2008 presidential primary, and it is truly an honor for him to get behind our campaign and cut ads for us across the commonwealth."

While the campaign noted in a press release that the ads will appear "across Pennsylvania" in the coming weeks, the radio hits began airing in the Philadelphia market this week.

–ABC News' Will McDuffie

A new super PAC backed by former President is injecting money into key 2022 races, investing $4 million in a new round of ad spending in battleground states, according to new financial data.

The series of seven- to eight-figure ad placements from super PAC Make America Great Again Inc. on Wednesday in Ohio, Pennsylvania, Arizona, Georgia and Nevada is a last-minute boost from Trump's team ahead of the . It follows months of criticism from Trump skeptics within the GOP that the former president is not spending enough to support 2022 GOP candidates, despite his massive fundraising power.

Wednesday's placements are the second round of ad spending by the new PAC, which was launched in late September and kicked off its first round of placements in the same Senate races earlier this month.

According to ad tracking firm Ad Impact, Make America Great Again Inc.'s biggest investment in the latest ad placement was a $1 million ad buy in the race between Democrat Tim Ryan and Trump-endorsed J.D. Vance in the Ohio Senate race, followed by $770,000 in spending on the rivalry between Democrat John Fetterman and Trump-endorsed Dr. Mehmet Oz in the Pennsylvania Senate race.

Read more here.

–ABC News’ Soo Rin Kim

There's the campaign Republicans are running on inflation, crime and the Biden agenda -- a sprawling and broad case against Democratic governance that's being adjusted to fit particular circumstances in races across the map.

Then there's the campaign Democrats are running -- on abortion rights and against far-right Republicans, but also at times against the Biden White House on the southern border and the handling of inflation and the urgency under which all that and more is being addressed.

Enter, again, President Joe Biden. He makes a rare-for-this-cycle trip to battleground Pennsylvania on Thursday to campaign for Democratic Senate candidate John Fetterman-- and also to provide messaging cover for the many Democrats he isn't campaigning for in person, either because of their choice or the constraints of time.

The streamlined messaging includes stronger commitments on abortion, including Biden's vow this week that, in January, he will sign a bill to codify Roe v. Wade -- contingent on holding the House and picking up at least two seats in the Senate.

–Read more here.

–ABC News’ Rick Klein

Senator Elizabeth Warren, D-Mass., is expected to campaign on Oct. 26 for Wisconsin Gov. Tony Evers, Lt. Gov. Mandela Barnes and state Attorney General Josh Kaul in what is the latest appearance by a prominent Democrat to rally voters weeks before the high-stakes midterms.

The events with Warren, first reported by ABC News, will also feature Wisconsin's Democratic senator, Tammy Baldwin.

Baldwin, Evers, Kaul and Warren will host an early voting event focused on young people near the campus of the University of Wisconsin at Madison, according to the Wisconsin Democratic Party.

Baldwin and Kaul are expected to walk with a group of students to an early voting location to cast their ballots.

Barnes is in a tight race to defeat incumbent Sen. Ron Johnson, a Republican.

Polling shows that Evers is in a toss-up race, too, against Republican challenger Tim Michels, with the latest FiveThirtyEight average showing Evers with less than 1% lead.

In a statement to ABC News, the Wisconsin Democratic Party Chair Ben Wikler said: "This election is deadlocked, and no one can sit this out. If Wisconsin students turn out to show the GOP they won’t let them trample on their rights, Democrats will win up and down the ballot. Senator Warren is an electrifying voice who will bring her incomparable energy and vision to mobilize Wisconsin students at exactly the moment it’s needed most."

In her own statement, Warren said, "Voters in Wisconsin know what is at stake in this election. Wisconsinites have the opportunity to vote for [Senate nominee] Mandela Barnes, Tony Evers, and Democrats all the way down the ballot who will fight to restore a woman’s right to choose, to bring down costs, to build an economy that works for all of us, and to attack the climate crisis head on. I’m proud to join them in this critical fight."

Warren joins a growing list of big-name Democrats -- including former President Barack Obama -- to hit the trail in various battleground states before Election Day.

They hope to counter the history of rough midterm elections for the party in power, plus major headwinds like high inflation, in part by focusing on Republican-backed restrictions on abortion and the extremism of some of the GOP nominees.

When asked by reporters after a gubernatorial debate on Friday whether former President Donald Trump planned to stump for the Republican ticket in Wisconsin, Brian Fraley, a communications specialist for the Michels campaign, said they would notify the press if such an event was scheduled.

Fraley said then that Obama coming to Milwaukee was a "sign" that the Evers campaign was "in trouble" because "they're calling in all the big dogs."

-- ABC News' Cheyenne Haslett and Paulina Tam