Trump faces a tighter race with Kamala Harris set to replace Biden, experts say

President Joe Biden's endorsement of Vice President Kamala Harris as the Democratic nominee for president has set the stage for a much tighter and uncertain race in November, according to some experts

Biden stepped down from the race Sunday as top Democrats pressured him to drop out following a disastrous debate performance and as Republican nominee Donald Trump was leading in the polls.

The Democrats had been headed for a "landslide defeat" in November, but now, they stand a chance, said Ian Bremmer, founder and president of Eurasia Group.

"They've turned [this race] around, and President Biden has given the Democrats a fighting chance," he told CNBC's "Squawk Box Asia" on Monday.

Harris now finds herself on a glide path to the Democratic nomination, though she will still need to win a majority of delegates ahead of the Democratic National Convention in Chicago in August. 

While some other contenders might throw their hat into the race, "it is very clear that Kamala Harris is the prohibitive favorite to become the nominee," Bremmer said. 

If Harris wins the nomination, she would offer the Democrats a "total reset," Steven Okun, senior advisor at McLarty Associates, said on CNBC's "Street Signs Asia."

"If the Democrats can be unified, come out of this convention, speaking with one voice, energized, excited, then they have a good chance to win in November," he said.

Allan Lichtman, a presidential historian who has correctly predicted the winner of every presidential election since 1984, told CNBC's "Capital Connection" that Harris would be in a "strong position to win the upcoming election" in a matchup with Trump.

He will wait until the Democratic convention to make his official prediction.

Harris said in a post on social media