Republicans in Vermont are deciding among four candidates who want to take on Democratic Gov. Peter Shumlin, who also serves as chairman of his party's national governors association. Other statewide offices, including an at-large House seat, also are on the ballot.
Vermont is one of four states where voters will cast primary and runoff ballots Tuesday.
Turnout was expected to be low in Vermont, where the polls are open until 7 p.m.
Dan Feliciano is a Libertarian, but he's running for governor as a write-in candidate in the Republican primary against three other candidates - Scott Milne, Steve Berry and Emily Peyton - whose names appear on the ballots. Milne, a businessman, is the favorite.
Meanwhile, Democrats were expected to nominate a write-in candidate - Progressive Dean Corren - for lieutenant governor after the only other candidate dropped out.
In Florida, former Gov. Charlie Crist is set to find out how much momentum he has for a political comeback, as Democratic primary voters appear ready to nominate the former Republican for a chance to reclaim his old job.
With a huge advantage in fundraising and name recognition, Crist is a heavy favorite over former Senate Democratic leader Nan Rich. The question is whether his victory margin will match those advantages or instead suggest that he's struggling to connect with core Democrats.
Republican Gov. Rick Scott is expected to coast to his party's nomination for a second term.
The Florida race has gained national attention both for Crist's resurrection attempt and Scott's struggles.
Scott, a wealthy health care executive who had never held public office before, won the job with less than a majority in 2010, and his first term has been marked by low approval ratings and struggles against the GOP-led legislature. Scott already has spent millions of dollars on ads criticizing Crist, pointing out how he has changed positions on same-sex marriage, gun control and President Barack Obama's health care plan to align with Democrats.
In Arizona, several Republicans are vying to succeed GOP Gov. Jan Brewer.
Brewer has put her muscle behind former Mesa Mayor Scott Smith. The pair appeared together at multiple campaign stops Monday trying to rally last-minute support. But state Treasurer Doug Ducey has painted himself as the front-runner in the race, citing a broad coalition of business leaders and other political figures. The field includes former GoDaddy executive Christine Jones and Secretary of State Ken Bennett, among others.
Democrat Fred DuVal is unopposed in his primary and will face the GOP winner in November.
Oklahoma Democrats will choose their Senate nominee in a runoff, with state Sen. Connie Johnson expected to top perennial candidate Jim Rogers. The winner becomes a general election underdog against Rep. James Lankford for the seat being vacated by retiring Republican Sen. Tom Coburn.