ABC's Shushannah Walshe and Jeff Zeleny report:

LOUISVILLE, Ky. - Former President Bill Clinton took center stage today in the most watched Senate race in the country, telling a crowd of 1,200 that "it makes a big difference" whether Kentucky Secretary of State Alison Lundergan Grimes wins in November.

"For the last 30 years, as often as not, their strategy has worked mostly because our people see it, get discouraged, and stay home, believe that it doesn't make a difference. And I am here to tell you - I know, it was my life - it makes a big difference who wins this election and Alison Lundergan Grimes should win it and will with your help," Clinton said to a roar from the crowd at a fundraiser and rally.

Grimes, who welcomed Clinton by proclaiming "Kentucky is Clinton country," is expecting to face off against Sen. Mitch McConnell, though the Senate minority leader is facing a primary challenge.

"We will send the message with this campaign, with the help of each and every one of you who are here today and those across the Commonwealth, that Mitch McConnell, he is out of touch, he is out of ideas, and come November with your help and support he will be out of time," Grimes, hoping to toss the senate minority leader out of office, said.

The attendees donated between $100 and $5,200 to see Grimes and Clinton stump together in his first campaign trail foray in 2014. There was also a smaller reception for high dollar donors who donated between $1,000 and $5,200, and a Grimes aide told ABC News the campaign raised $604,000 today.

Grimes, who was in first grade when McConnell first became a U.S. senator, recalled when she was 14 years old and greeted the new president in Washington with a bouquet of roses, telling the audience the moment "stuck with me for ages" and the "memories they flood back in."

Wearing a red suit and speaking before Clinton, Grimes jabbed McConnell over and over on issues including raising the minimum wage and pay equity saying his "idea of a jobs plan is millions upon millions of dollars coming into the state of Kentucky from his Washington cronies in the form of attack ads."

"Mitch McConnell just doesn't get it - but we get it. And over the course of this campaign, we'll show him," Grimes said, while Clinton watched and smiled from the side. "I believe or I wouldn't be standing here today, that Kentuckians don't view this race as a tossup. We are ready to toss out our senior senator."

Clinton, a longtime friend of the Lundergan family who Grimes called an "adviser," "mentor" and "friend" has advised the 35-year-old candidate throughout the process and even said today he has read through her jobs plan. Clinton first appeared in a video at Grimes' official campaign kickoff last summer.

Campaign cameras were on hand to capture the duo campaigning together, likely to make it into a future campaign ad.

Clinton told the crowd Kentucky has been "good" to him, reminding them the state voted for him twice - in 1992 and 1996 - and for his wife, the once and possibly future presidential candidate Hillary Clinton, in the 2008 Democratic presidential primary, over Barack Obama.

One name Grimes did not mention during her speech was President Barack Obama. In an interview with ABC News, Grimes was asked why Clinton is such a bigger draw. She answered that the 42nd president has been "involved in this campaign literally since day one."

"He is someone who has literally seen me grow up since I was 14 years old. And today having someone who has such a distinguished record of economic expansion…make this his first campaign stop of the 2014 election cycle, to endorse our jobs plan…I think it speaks volumes about not only the priority that Kentucky is, his commitment and friendship obviously with my family which we are so grateful for, but most importantly that here in Kentucky he is backing the jobs candidate," Grimes said.

When asked if there is anything from the Obama administration that she can run on in a positive way, Grimes mentioned the killing of Osama Bin Laden, and "paycheck fairness."

"But in many respects there are disagreements between the president and how his policies have impacted Kentucky, disproportionately negatively impacting a large region of our state," Grimes said. "This campaign though is one that is Kentucky based, through and through."

Just after Clinton and Grimes spoke, McConnell said on Capitol Hill that he "welcome(s)" Clinton back to the Bluegrass State.

"Last time he ran in 1996 he eked out a narrow victory while I beat the current governor in Kentucky by 160,000 votes, 10 points," said McConnell, who also has a primary challenger in the race, said. "In 2008, both Bill and Hilary came to town, including the day before the election, and I won by 100,000 votes. So I welcome President Clinton back to Kentucky. Every time he has come it has been really good for me."

McConnell will face off against his conservative opponent, Matt Bevin, in May.

ABC News' Avery Miller and Christopher Good contributed to this story.

(Credit: Timothy D. Easley/AP Photo)