Arguably, the most important U.S. Senate race this year is in Nevada, where incumbent Republican Dean Heller is fighting against intense Democratic opposition for the seat that could decide which party controls the Senate next year.

Republicans need a net gain of four seats to regain control of the Senate, which they lost after 2006. Mr. Heller's seat and Scott Brown's seat in Massachusetts are two of the most critical for the GOP to hold. There are currently 47 Republican senators, 51 Democrats and two Independents, both of whom caucus with Democrats.

Mr. Heller spent Wednesday in Orange County, meeting with business and political leaders, building relationships and raising funds. California, and Orange County, in particular, are key fundraising stops for Republicans across the country. Democrats also raise significant funds in the county; President Barack Obama held a fundraiser last week in Corona del Mar.

Mr. Heller, 51, appointed by Nevada Gov. Brian Sandoval after Republican Sen. John Ensign resigned in April amid ethics investigations, has a long political résumé in Nevada as a member of the House of Representatives, the state Assembly and a former secretary of state.

And Mr. Heller's message is in line with conservatives, particularly on economic issues. He voted in the House against TARP — the 2008 government bank bailout — and fervently supports a balanced budget amendment to the Constitution. He also told us he is "in favor of guest-worker programs and expanding such programs," which may appeal to Latino voters in Nevada.

The Nevada Senate race is a potential battle royale because the stakes are so high. Nevada's other senator, Democratic Senate Majority Leader Harry Reid, undoubtedly will commit significant resources to winning the seat for his party. Mr. Heller said, "We are really running against Harry Reid ... he wants this seat bad."

Also, Nevada has a slight Democratic edge in voter registration, and Mr. Heller's opponent is a prominent Democrat, seven-term Rep. Shelley Berkly.

Anyone rooting for a Republican takeover in the Senate, and perhaps a counterbalance to an Obama second term, should focus on Nevada and Mr. Heller's campaign.