Former President Donald Trump may be able to clinch the Republican presidential nomination on Tuesday, after results are in from the four GOP voting contests taking place in Georgia, Washington, Mississippi and Hawaii. 

Georgia, Mississippi and Washington are all holding primaries, while Hawaii is holding caucuses.

Trump's remaining major rival, former United Nations Ambassador Gov. Nikki Haley, dropped her White House bid after the Super Tuesday primaries. 

Trump dominated the Republican field without ever debating any of his primary opponents, and none of them ever surpassed him in early-state polling.

The former president is also entering the general election phase of the presidential campaign facing 91 felony charges in four criminal cases. His first criminal trial is slated to begin on March 25 in New York, where he faces 34 charges connected to alleged "hush money" payments to adult film star Stormy Daniels during the 2016 presidential election. Trump also faces state criminal charges in Georgia for alleged interference in the 2020 presidential election, as well as federal charges in Washington, D.C. He is also facing federal charges in Florida over his handling of classified documents after his presidency.

In the four contests Tuesday, 161 GOP delegates are at stake. Trump has over 1,075 delegates, according to CBS News estimates, and is closing in on the 1,215 delegates needed to secure the nomination. 

Trump would be the first Republican in history ever to secure the presidential nomination three straight times. Richard Nixon won the GOP nomination three times, although not in consecutive cycles.

In Georgia, 59 delegates are on the line. In Mississippi, 40 delegates are in play. In Washington, that's 43 delegates. In the Hawaii caucus, 19 delegates are up for grabs. 

When do polls close for today's GOP primaries?

Georgia

Polls open at 7 a.m. and close at 7 p.m., but any voter in line at 7 p.m. will be able to cast a ballot, according to state rules. 

Mississippi

Polls open at 7 a.m. CT (8 a.m. ET) and close at 7 p.m. CT (8 p.m. ET) but as in Georgia, any voter in line at 7 p.m. will be able to cast a ballot. 

Washington

Washington is a mail-in voting state, but voters may also cast ballots on Tuesday. Polls close at 8 p.m. PT (11 p.m. ET).

Hawaii

Hawaii GOP caucus goers will go to their caucuses from 6 p.m to 8 p.m. local time (12 a.m. to 2 a.m. ET).

How many delegates does Trump need to secure the nomination?

He needs under 140 delegates to reach 1,215. 

How many delegates does Trump have? 

Here is the latest delegate estimate from CBS News' data desk:

Kabir Khanna contributed to this report.