We recently had two elections (New York and Nevada) that went to Republicans. There were no presidential candidates on these ballots. The contests were decided on what those candidates stood for and how well they got their message out to the voters. Moreover, these districts had previously been won by a Democrat. This may be a bellwether on the next presidential election.
Obama has a declining approval rate, at present it is well under fifty percent. If it stays there, or goes any lower, the odds are that he will lose the election. If he loses the election the question becomes, how large are his coattails? If they are large, many Democrat congressmen and senators are in danger of losing their elections.
Democrat realists are already determining what what will happen in the upcoming presidential election. Some are quite worried that Obama is doing nothing to improve the economy, just making it worse. They are concerned that the Obama name on the ticket cannot help them. This is particularly true in swing districts and swing states.
The Obama machine just continues to put out more of the same and it is not enough to improve the economy. That is why Hillary is becoming more important to Democrats, and why we are hearing more about her at this time. Liberals want to win the next election and will do whatever it takes to win. They have made fantastic strides in their agenda under Obama. However, politics is politics, and liberals may decide that Obama cannot win (putting their control of the senate in jeopardy) then it is time to get a candidate that can win. We will be hearing more about Hillary as we get closer to the election.