This week started with a bang, as one Democratic Senate primary challenger jumped in Monday morning and one jumped out that night. Sen. Blanche Lincoln (D-Ark.) becomes the third Democratic senator to face a serious primary challenge this year -- the other two are Arlen Specter (Pa.), who switched parties last year, and Michael Bennet (Colo.), who was appointed to the seat last year.

Here's a look back at the week that was in 2010 midterms:

SENATE

ARKANSAS: Lt. Gov. Bill Halter entered the Democratic primary race Monday morning by releasing a video announcing his challenge to Sen. Blanche Lincoln, who was already facing a difficult November -- and now will struggle just to get past May 18. Halter spoke with RCP in an interview on Tuesday, during which he struck a populist tone. A general election poll released this week found Lincoln making significant gains against several Republican challengers, but she's still polling mostly in the 30s.

ILLINOIS: Democratic nominee Alexi Giannoulias conceded this week that the bank his family owns will likely fail before the November election -- a potentially dangerous blow to his electoral hopes. He tried to get out in front of the story this week, sitting down with the Chicago Sun-Times and Tribune editorial boards for more than an hour each to answer questions. However, as the Sun-Times' Mark Brown wrote Thursday, "certain unpleasant facts remain" about the situation, and then there's also this: His only qualification for running for state treasurer in 2006 was his experience as CEO of what's a now-failing bank, and he concedes he was partially responsible for it.

NEVADA: Could things get any worse for Sen. Harry Reid (D)? Probably, but as of now they're pretty bad. A Mason-Dixon poll out at the beginning of the week found Reid trailing all three of his potential GOP opponents by double-digits. Against former state GOP Chair Sue Lowden, Reid did not even garner 40 percent support. However, Tea Party of Nevada candidate Scott Ashjian filed his candidacy papers this week, causing Republicans some worry he could split the conservative vote in November. And rumors persist that he's a Democratic plant aiming to help Reid get elected, though he denies that.

NEW YORK: There was plenty of polling here this week, despite the fact that Republicans have no clue who's going to run against Sen. Kirsten Gillibrand (D). Rasmussen's poll found Gillibrand leading former Gov. George Pataki by 2 points, while Marist found Pataki up 3 points. Either way, most insiders don't expect Pataki to run, and Daily News owner Mort Zuckerman announced he was out as well. Marist pollster Lee M. Miringoff believes Ford's interest in the race may have "solidified" Gillibrand's support among Democrats.

NORTH DAKOTA: Democrats took a hit here this week, as former Attorney General Heidi Heitkamp announced she would not run against the GOP frontrunner, Gov. John Hoeven. The seat came open at the beginning of the year when Sen. Byron Dorgan announced he would not run for re-election. Rep. Earl Pomeroy (D) briefly considered running, but opted for re-election instead. State Sen. Tracy Potter appears to be the most likely Dem nominee at this point.

PENNSYLVANIA: Sen. Arlen Specter (D) found himself in unusual territory this week -- in the lead. A new Quinnipiac survey showed him ahead of likely Republican opponent, former Rep. Pat Toomey, by 7 points. The poll also found him leading his primary challenger, Rep. Joe Sestak, by 24 points.

GOVERNOR

TEXAS: Gov. Rick Perry (R) leads the first post-primary poll by 6. Sen. Kay Bailey Hutchison (R) made history in her primary loss. The DGA thinks Perry is "strikingly vulnerable." With no runoff, the general election campaign started in earnest. The Perry camp played the L-word, while White said Perry failed as gov. Perry says Hutchison should stay in the Senate.

NEW YORK: Attorney General Andrew Cuomo actually gained ground on Rick Lazio despite the Paterson mess; his job approval sky high.

CALIFORNIA: Attorney General and former Gov. Jerry Brown (D) made his comeback bid official. On his media tour, he stressed his experience and paved a centrist course; he even did some pullups. His long record: "a blessing and a curse." He targeted Meg Whitman with the AP. Whitman hit Steve Poizner in a radio ad.

FLORIDA: Alex Sink (D) targets Bill McCollum (R) over Medicaid fraud. Both candidates responded to Gov. Charlie Crist's (R) final state of the state address.

MICHIGAN: Rep. Peter Hoekstra (R) took a lead in the GOP primary in Michigan. Mike Huckabee endorsed Attorney General Mike Cox (R). The Democratic field shrinks by one.

ILLINOIS: It's decision day in the GOP primary, with a recount or a concession coming. Looking ahead, state Sen. Bill Brady "swung and missed" while trying to hit Gov. Pat Quinn (D), the Tribune says.

GEORGIA:Ex-Georgia Gov. Roy Barnes (D) has a slight lead over GOP foes. Rep. Nathan Deal (R) is delaying his resignation to vote on health care.

THE REST: Charlie Baker (R) leads the field in the Massachusetts money chase. PA Attorney General Tom Corbett leads all potential Democratic foes. Rasmussen finds former Sen. Lincoln Chafee (I) leading in Rhode Island. John Stephen (R) entered the New Hampshire governor race. Wyoming Gov. Dave Freudenthal (D) decides not to challenge the term limit law, giving the GOP an opening.

HANDICAPPER WATCH
Cook Political Report:
*Texas Gov from Lean R to Toss Up.
*NC-08 from Lean D to Likely D.
*AR-01 from Lean R to Toss Up
*AL-02 from Toss Up to Lean D.
*NY-29 from Lean D to Lean R

Rothenberg Political Report:
*TX Gov from Clear Advantage R to Narrow Advantage R
*NY-29 from Lean D to Toss Up
*MA-10 from Safe D to D Favored.

--Kyle Trygstad and Mike Memoli