Former president Bill Clinton is wading into a Democratic primary — against the wishes of the Obama administration.

Today in Colorado, Clinton endorsed Andrew Romanoff, the former speaker of the state house. Romanoff is challenging Sen. Michael Bennet, an Obama ally, in a heated Democratic primary. This is the first time that Clinton has actively campaigned against an Obama-backed candidate. Usually, he is a team player: Earlier this year, he backed Sen. Blanche Lincoln (D., Ark.) in her primary. He even helped Obama to try and persuade his old friend, Rep. Joe Sestak (D., Pa.) from challenging Sen. Arlen Specter (D., Pa.).

Clinton, who carried Colorado in his 1992 presidential run, says Romanoff gives Democrats the “best chance” to hold the seat. Maybe not — as Politico reports, “an automated SurveyUSA poll taken earlier this month showed Romanoff with a steep hill to climb against Bennet. . . Bennet took 52 percent support in the poll, compared with 36 percent for Romanoff.”

Bennet was appointed to the seat last year by Gov. Bill Ritter after former Sen. Ken Salazar was named interior secretary by Obama. Since then, his campaign has been boosted by Obama, who’s stumped for the incumbent, and by the Democratic Senatorial Campaign Committee, which has ladled Bennet heaps of cash.

Why is Clinton stepping in? Jeff Zeleny reports:

In the 2008 presidential race, Mr. Romanoff was among Hillary Rodham Clinton’s biggest supporters in Colorado. (Mr. Bennet supported Mr. Obama.) The endorsement on Tuesday, according to associates of Mr. Clinton, stemmed from Mr. Romanoff’s support of Mrs. Clinton.
The former president explained that he met Mr. Romanoff in 1992, while Mr. Romanoff was a student at the Kennedy School of Government. Mr. Clinton said that Mr. Romanoff worked tirelessly to help Democrats carry Colorado four years later.

Dick Wadhams, the state-GOP chairman, tells National Review Online that Clinton’s endorsement “reveals the soft underbelly of the Bennet candidacy.”

“Even as a U.S. senator, Bennet has not been able to lock in his party’s nomination, much less connect with the voters,” Wadhams says. “While I still think that he’ll limp his way to the nomination, this is just another indication of how inherently weak he is as a candidate.”

Still, Wadhams says the GOP can win the seat, regardless of whether Bennet or Romanoff secures the party nod. “There’s not a dime’s worth of difference between the two on the issues,” Wadhams says. “Romanoff is trying to make the case that he’s more liberal, but it’s not very compelling. . . One is a liberal legislator from a very liberal district in the middle of Denver and the other is a liberal senator in Washington who woke up one day and found himself a senator thanks to the benevolence of Bill Ritter. We can build cases against both statewide, especially this year.”

While Bennet is struggling, Romanoff has his own problems. As CNN reminds us, “earlier this month Romanoff said that a senior White House aide suggested last year that three administration jobs might be open to him if he abandoned plans to run against Bennet. But Romanoff also noted that he was never offered a position by the White House.” Debate over Romanoff’s handling of the issue hasn’t helped him on the trail.

The GOP Senate primary, between Jane Norton, a former lieutenant governor, and Ken Buck, a prosecutor, is a “real race,” Wadhams says. “It’s truly competitive.” You can read more about the GOP primary here.