Republicans not otherwise occupied by the prospect of Mitt Romney slipping further behind President Obama have the option of being equally pessimistic about their party’s chances of retaking the Senate. A Politico feature and an analysis in the New York Times by blogger Nate Silver both highlight the raft of recent polls that show that the GOP’s once bright hopes of capturing the upper chamber from the Democrats have declined precipitately in the last month. But any attempt to pin the blame for this trend on the party’s presidential candidate is probably a mistake. There are states in which Romney will not help the rest of the ticket, but if Republicans wind up losing the Senate it will not be his fault alone.

That the odds have now shifted in favor of the Democrats retaining control of the Senate is not in dispute. As we all know, a certain GOP pickup in Missouri became a likely Democratic hold the moment Todd Akin opened his mouth to talk about rape victims. But the Akin fiasco highlights an important truth about imposing a national narrative on what is essentially a series of separate elections. Attempts to wrap a number of different races with different candidates in different states are almost always something of a stretch. When you break down what is happening in the various Senate races, what we are seeing often has more to do with local factors than with Romney’s problems.

Republicans came into 2012 with a decided advantage in the battle for the Senate, as Democrats had to defend 23 seats to the Republicans’ 10. Democratic seats in Nebraska and Missouri were seen as likely losses while six others were toss-ups.  On the GOP side of the aisle, only Scott Brown’s hold on Teddy Kennedy’s old seat in Massachusetts was considered questionable.

Since then, Olympia Snowe’s retirement has moved one GOP seat from a likely hold to a likely Democrat pickup. Along with the Akin fiasco in Missouri, Democrat seats in Florida and Hawaii that were seen as very competitive races are now starting to look like easy Democrat victories. But even if we accept those outcomes as set in stone, that still gives us a Senate tally that is current 48 likely Democrats and 44 likely Republicans, leaving eight seats that are still very much in play for both parties.

That means there is plenty of room for a number of different possible outcomes. But while the remaining tossups in Connecticut, Massachusetts, Virginia, Indiana, Wisconsin, North Dakota, Montana and Nevada are bound to be affected by the Obama-Romney battle, the outcome in each will be more a function of the individual candidate’s strengths than any coattail or drag effect coming from the top of the ticket.

If Romney does fade in the final weeks, the assumption is that the impact in the two New England battlegrounds where Republicans never expected to win at the presidential level, Connecticut and Massachusetts, could be disastrous. But both Linda McMahon (who has put a Connecticut seat in play that most had assumed was safe for the Democrats) and Scott Brown are already running on the assumption that ticket-splitting Democrats are the key to victory. If anything, the perception that Obama is a shoe-in could help rather than hurt them since it would put less pressure on wavering Democrats to stay in the fold.

If Republican hopefuls are fading down the stretch in other tossup states, it will be equally hard to pin their troubles on Romney. The inability of GOP challengers in North Dakota and Montana to oust seemingly vulnerable Democratic incumbents in red states has to do with their own weaknesses, not those of Romney. In Nevada, the problem may be the resilience of Democrat Shelley Berkley, whose popularity seems to have withstood an ethics investigation, even though Republican Dean Heller still holds a small lead. And in Indiana, the failure of Tea Party favorite Richard Mourdock, who ousted longtime GOP incumbent Richard Lugar in a primary, to win over independents has placed that seat in jeopardy for the Republicans, though they are still ahead there.

That leaves two seats where the Romney factor might be decisive.

Both Wisconsin and Virginia are presidential tossups. Currently President Obama leads in both and it is arguable that his strength is helping Tammy Baldwin and Tim Kaine stay ahead of Tommy Thompson and George Allen. Should the Democrats win both these seats it will be reasonable to assume that distaste for Romney and enthusiasm for Obama helped make the difference there.

However, even there the results will be more about the inability of Thompson and Allen to seal the deal with voters than anything Romney does.

When there is a decisive result in Congressional and Senate races, the impulse is to always assume a national trend. But even in years when there is such a trend, such as 1994, 2006 or 2010, it is important to remember that such party victories are usually the aggregate result of an assortment of local factors more than one national issue. That’s why a Republican failure to take the Senate this year will have a lot more to do with Akin, Allen and Thompson than it does with Romney.