Voters head to the polls in Arizona, Utah and Idaho on Tuesday, in a series of contests that could help determine whether Republicans will be able to stop GOP front-runner Donald Trump's path to the nomination.
Both Democrats and Republicans hold primaries in Arizona and caucuses in Utah; Democrats will also caucus in Idaho. (Republicans held their Idaho caucuses on March 8.)
Hillary Clinton or Bernie Sanders are the two candidates in the Democratic race while three contenders remain in the Republican race: Donald Trump, Ted Cruz and John Kasich. The last GOP candidate to drop out was Marco Rubio, who exited the race last Tuesday after a disappointing finish in his home state of Florida.
Watch CBSN for coverage of Super Tuesday at 10 p.m. ET
The Idaho Democratic caucuses will occur from 9 p.m. ET to 11 p.m. ET. Polls close in Arizona at 10 p.m. ET. In Utah, Republican caucuses begin at 9 p.m. ET and are expected to finish at around 11 p.m. ET; however, online voting remains open until 1 a.m. ET. Democratic caucuses in Utah are expected to finish at around 10:30 p.m. ET.
For Republicans, 98 delegates are up for grabs; for Democrats, the number is 149. Democrats' delegates are awarded proportionally throughout the primary process; for Republicans Arizona's delegates are winner-take-all, while Utah's are winner-take-all if one candidate receives at least 50 percent of the vote.
Though there hasn't been extensive polling in either race, Cruz is favored to win the Utah caucuses. Trump has led in most polling of Arizona, and has the backing of Maricopa County Sheriff Joe Arpaio and former Arizona Gov. Jan Brewer.
These four contests come the week after Trump picked up victories in Florida, North Carolina and Illinois, helping increase his delegate lead over his GOP opponents. On the Democratic side, Clinton had a clean sweep of all five states voting last week (Ohio, Florida, Illinois, North Carolina, Missouri), widening her delegate lead over Sanders to a point that some Democratic observers (and Clinton's campaign) have called it insurmountable.
According to CBS News' latest count, Trump has 676 delegates, with Cruz at 406 delegates and Kasich at 143 delegates. For the Republicans, a candidate needs 1,237 delegates in order to clinch the nomination. On the Democratic side, Clinton has picked up 1,580 delegates while Sanders has accumulated 819 delegates. A candidate needs 2,383 delegates in order to win the nomination.
The last time the candidates debated on either side was before the March 15 primaries; Republicans had a planned debate in Salt Lake City on Monday, sponsored by Fox News, but it was canceled when both Trump and Kasich said they would not participate.