The term coattails is the most vivid literary analogy in American politics, but also the most deceptive. Coattails convey that because voters support the top of the ticket, they will automatically hold on, voting for that party’s down ballot candidates. Yet that is not how it works:  coattails are a function of grassroots turnout, not a top down down phenomenon. 

Coattails come into play, when the top of the ticket draws either new voters to the polls, or pulls voters away from prior partisan loyalties. Eisenhower in 1956 and Nixon in 1972, despite huge landslides, had no coattails. Their victories were premised upon sponging up Democratic votes, not transforming the underlying balance of electoral power. Yet, Reagan in 1980 and Obama in 2008, with lesser margins, generated coattails.

Under Reagan the GOP expanded the entrance of Evangelical voters to the electorate and largely severed White Catholic loyalties to the Democrats.  Obama’s coattails were premised upon a double play:  increasing the shares of the total vote cast by minorities and younger voters and carrying those voters by landslide margins. These key voting blocs turned out by their enthusiasm for Reagan and Obama came to the polls with a predisposition to support Republicans in 1980 and Democrats in 2008.

In 2008, in Virginia, exit polls showed that the Black and the under 30 votes each swelled to a 20 percent share of that state’s electorate. Meanwhile, in Virginia’s 2009 gubernatorial election, exit polls showed that Black’s and under 30 voters each melted to a 10 percent share. This year, where the Obama campaign takes Virginia’s Black and under 30 voters, will probably be dispositive in determining whether Allen or Kane wins that hard fought Senate contest, long deadlocked in the polls. This coattail effect could well determine the outcome in the closely contested Senate contests all across the nation.

Which leaves common sense as a factor in measuring the allocation of resources in the post Citizen’s United world of big money flooding into campaigns.  On the Republican side, will the hundreds of millions of dollars at the disposal of Rove’s Crossroads, the Chamber of Commerce and pro-GOP super PACs like Americans for Prosperity, fund the proper balance between presidential and congressional races? The legal restrictions on de facto coordination, while porous, could still lead to unproductive allocations for the GOP candidates.

On the congressional side, Democrats need to take advantage of any openings where the Tea Party produced vulnerable Republican candidates for the general election. In 2010, the Democrats would have probably lost the Senate if the comparatively moderate Republican frontrunners had not lost primaries in Delaware, Colorado and Nevada, which in turn would have enabled the GOP to concentrate huge resources into the Washington state race won ever so narrowly by Democratic Senator Patty MurrayPatricia (Patty) Lynn MurrayOvernight Health Care — Sponsored by PCMA — Trump official won't OK lifetime limits on Medicaid Dems warn against changes to federal family planning program Overnight Health Care: Drug company under scrutiny for Michael Cohen payments | New Ebola outbreak | FDA addresses EpiPen shortage MORE.

In 2012, Tea Party surges in Senate races have produced vulnerable GOP candidates in Indiana (Mourdock), Missouri (Akin) and Montana (Rehberg), states trending Republican. Yet, in the most recent second quarter campaign finance reports, Massachusetts’ Democrat Elizabeth WarrenElizabeth Ann WarrenJuan Williams: Trump gives life to the left Elizabeth Warren urges grads to fight for 'what is decent' in current political climate Tomi Lahren responds to genealogist's investigation of her family: 'She failed miserably' MORE raised $8.67 million, while fellow Democrats McCaskill from Missouri raised $2,435 million, Tester from Montana raised $1.068 million and the challenger Donnelly from Indiana, raised just shy of $900,000.

While Warren’s challenge to Senator Brown in the Bay State is critical for the Democrats’ prospects for maintaining their narrow Senate majority, the question becomes will candidates like Indiana’s Joe DonnellyJoseph (Joe) Simon DonnellyVoters Dems need aren't impressed by anti-waterboarding showboating Overnight Defense: Senate confirms Haspel as CIA chief | Trump offers Kim 'protections' if he gives up nukes | Dem amendments target Trump military parade Hillicon Valley: Lawmakers target Chinese tech giants | Dems move to save top cyber post | Trump gets a new CIA chief | Ryan delays election security briefing | Twitter CEO meets lawmakers MORE have the resources for transforming a competitive Senate race into an upset victory?  In short, will Democratic contributors have the discipline to make the Tea Party once again cost the GOP control of the Senate? If Demint’s Tea Party wing in the Senate grows while becoming a part of the majority, the Democrats will have missed an opportunity. 

In the final analysis, as we head toward the home stretch in November, we should be focusing on how coattails really work and which party best uses common sense in the allocation of precious resources in the key congressional races.      

Gyory is a political consultant with Corning Place Communications in Albany, New York and an adjunct professor or political science at the University of Albany