Until the Blagojevich scandal broke, Barack Obama looked to be on his way to a presidential honeymoon (though not a mandate). Now, however, things look less clear.

Just a few days ago, Obama’s approval numbers were remarkable, as CNN noted:

A new national poll suggests that Barack Obama’s having one heck of a honeymoon.

Nearly eight in ten Americans questioned in a CNN/Opinion Research Corporation survey out Tuesday morning are giving the president-elect the thumbs up when it comes to his handling of the transition. Seventy-nine percent approve of Obama’s performance so far during transition, with 18 percent disapproving.

Obama’s approval rating is “14 points higher than the approval rating for president-elect Bush in 2001 and 17 points higher than president-elect Clinton’s rating in 1992,” CNN Polling Director Keating Holland noted.

Rasmussen found a similar uptick in approval of Obama from 52% just after election day to 67% yesterday. The shift has consisted almost entirely of growth in the number of people saying they approve of Obama’s performance but do not strongly approve — a finding which is consistent with a honeymoon.

The reason for this shift is relatively simple: Republicans are largely refraining from criticizing Obama, which limits negative news coverage since reporters often frame such stories around the president’s critics. The flow of information to the public about him has therefore become overwhelmingly positive, which has driven up his approval numbers. As Jim Stimson explains in Tides of Consent, this is the classic pattern of presidential honeymoons.

Now, however, the Obama administration has to be concerned that the Blagojevich scandal could undermine the honeymoon before it has even really begun. My research (PDF) suggests that efforts to link Obama to the scandal are likely to fail in the current political climate, which features relatively high approval of Obama among opposition party identifiers. However, the controversy and the questions that are being asked about Obama’s role (if any) may draw out Republican criticism, returning the political climate to a two-sided message flow that will ultimately deflate Obama’s approval numbers. That’s what happened to Bill Clinton — early controversies concerning his appointments and gays in the military encouraged his opponents to speak out against him, which ended any chance he had of a honeymoon.

It’s too soon to say, of course, whether Blagojevich will have any significant effect on Obama, but the downside risk is real.

Update 12/12 9:47 AM: Via Media Matters, here’s an example of how the scandal is emboldening Republicans to restart the flow of negative information about Obama:

Although prosecutors said Mr. Obama was not implicated in their investigation, the accusations of naked greed and brazen influence-peddling have raised questions from some about the political culture in which the President-elect began his career.

Republican leaders, sensing an opening, have raised questions about Mr. Obama’s relationship with various players in the Illinois political drama, and criticized Mr. Obama’s first remarks on Mr. Blagojevich as vague. They have urged Mr. Obama to divulge any contacts between his staff and the governor’s administration.