ABC News' new Frustration Index stands at 67, higher than the estimated level of 63 in 1994 when Democrats lost Congress and the GOP regained control of Congress, and in 2006 when Democrats took it back. In contrast, a lower Frustration Index has been favorable to incumbents. In 1998, when the estimated Frustration Index stood at 39, the reelection rate for incumbents was 98 percent.
Incumbents across the country are feeling the heat from voters. Like Reid, Arkansas' Democratic Sen. Blanche Lincoln may be facing the toughest political fight of her political career.
Lincoln will face off against Lt. Gov. Bill Halter in a runoff primary today, and if she loses, she will become the third U.S. incumbent senator to be voted out, after Sen. Arlen Specter, D-Pennsylvania, and Sen. Bob Bennett, R-Utah.
No more than one U.S. senator has lost a primary since the 1980 election, when four incumbents were defeated in intraparty fights.
In the May 18 primary, Lincoln didn't get the 50 percent of votes needed to win the Democratic seat outright, pitting her once again against Halter, whose received millions of dollars from labor unions opposing Lincoln.
Both President Obama and former president Bill Clinton have endorsed Lincoln, but voter discontent with incumbents remains high in Arkansas.
Republican women are leading in California, where former Hewlett-Packard chief executive Carly Fiorina has a substantial lead in the Senate primary, and former Ebay chief executive Meg Whitman is leading the race in the gubernatorial nomination.
Whitman spent more than $70 million of her money in her campaign to succeed Gov. Arnold Schwarzenegger, a moderate Republican.
In South Carolina, adultery allegations don't seem to have hurt gubernatorial candidate Nikki Haley, who still has a double digit lead in her race.