Republican candidates for the Senate in Oregon, Louisiana, North Carolina and elsewhere have de facto given up on John McCain and are urging voters to support them as a counterweight to President Obama. They say that one-party rule is bad for the country. Interestingly enough, in 2004, when Republican control of Congress was assured, few Republicans were advocating a vote for John Kerry in order to prevent the dreaded one-party rule. In 2000, 85% of the people voted for the same party for the Senate as for President, so in practice, people do not really split their tickets just to give each party some power. In fact, when Congress and the White House are controlled by different parties, everyone bemoans "the gridlock in Washington." (2004 data weren't available).
http://electoral-vote.com/