Outlets like Politico continue to write about the race to control the Senate as one in which the Republicans have blown their chance to win an easy victory. It’s true that sure GOP wins have been lost. The Todd Akin fiasco will probably cost them a once-sure pickup of a seat in Missouri and Olympia Snowe’s decision to retire will likely mean a pickup for the Democrats. But a look at Real Clear Politics’ Senate map shows that there’s still plenty of doubt as to whether it will be Harry Reid or Mitch McConnell sitting in the majority leader’s chair next January. With 12 races rated as a tossups and with a Florida seat now called as a likely Democratic win, though still competitive, this is no time for either side to be making assumptions about the outcome on Election Day. Each race needs to be judged on its own merits and the particular circumstances in that state, but the impact of the presidential race will be crucial.

The odds are there will be no partisan sweep like the midterm victories of the Republicans in 1994 and 2010 or the Democrats in 2006. Nor does is seem likely that either presidential candidate will have the kind of coattails that will create a landslide that will radically affect the composition of Congress. But that doesn’t mean the fates of President Obama and Mitt Romney won’t materially impact the various Senate races. With so many Senate races too close to call, the ability of either candidate to create any kind of a groundswell down the ticket will probably be the difference. Though there are too many variables to be sure of anything this year, the party that wins the White House is likely to be the one that controls the Senate as well.

The fact there are an almost unprecedented number of competitive Senate races this year is a function of the Democrats’ big win in 2006 when they seized control of the upper house for the first time since 1994. That set up 2012 as a year in which they would have to defend far more seats than the Republicans, including some in states like Virginia, Montana, and Missouri where they would be underdogs. Thanks to George Allen’s problems in recapturing his old mojo in Virginia and Todd Akin’s unfortunate discussion of pregnancy and rape, things aren’t lining up quite so easily for the Republicans.

However, this campaign may turn out to have as many pleasant surprises for the Republicans as it has disappointments.

Joe Lieberman’s old seat in Connecticut was thought to be a layup for the Democrats, but thanks to Linda McMahon’s unexpected strength and a weak Democrat like Chris Murphy, it may turn out to be a GOP pickup.

In Ohio, Democrat Sherrod Brown looked to be a shoe-in against young Josh Mandel, but the Republican’s staying power in the polls is scaring Democrats.

Even in blue Pennsylvania, the Democrats have their Senate worries. Bob Casey beat Rick Santorum by a whopping 18 percentage points in 2006, but now polls show him with a slim lead over largely unknown Tea Partier Tom Smith. The Republican may not be able to close that gap, but if Romney, who is also trailing by only a few points, gains more ground in the coming weeks, Smith may be dragged along with him.

All three of these states may wind up staying in the Democratic column, but a strong showing for Romney in all of these states is likely to give a boost to all those Republican candidates. Even though he won’t win Connecticut, if he makes it close, that could be enough to also make the difference for McMahon, who is running ahead of the top of the ticket right now. The same is true elsewhere. If Romney’s surge isn’t derailed by the last debate, it will be interesting to see whether he is able to create a tide that will lift all GOP boats. All 12 of those tossups and even the Florida seat that Bill Nelson looks to be holding onto right now are as much in play as the presidency itself. Which means there is a good chance that the next president, no matter whether his name is Obama or Romney, will be able to count on a slim majority in the Senate next year.