WASHINGTON — As the country’s two major political parties prepare to face off in what is expected to be a base-driven presidential election, the percentage of voters who identify as Democrats is at the lowest point in more than half a century.

A Gallup poll released Monday found 29 percent of Americans called themselves Democrats last year, down from the previous low of 30 percent in 2014.

It’s the lowest percentage since Gallup began asking about political affiliation in 1951.

Just eight years ago, when then-Sen. Barack Obama was running for president, the figure was 36 percent.

“It’s bad news for the Democrats to go from what appears to be the 36 percent high-water of the Obama administration down to 29. That’s not a good sign for them,” said political-science professor Dan Palazzolo of the University of Virginia.

“It’s a sign of decay of the public’s view of party affiliation,” he added. “People either psychologically or instinctively don’t want to be called one of the parties. Both parties are, in some ways, really not popular.”

The GOP didn’t fare much better, with just 26 percent of voters describing themselves as Republicans, one tick up from the all-time low of 25 percent in 2014.

Party identification for the GOP has been on a downward slide since 2004.

Independents, on the other hand, have been on the rise.

The poll found 42 percent of Americans didn’t affiliate with any political party, down from the all-time high of 43 percent in 2014. The number of Americans calling themselves independents has been at or above 40 percent for the last five years.

“Americans’ attachment to the two major political parties in recent years is arguably the weakest Gallup has recorded since the advent of its polls,” said Gallup’s Jeffrey Jones.

Polling organization note that many independents actually have a political leaning toward one of the parties.

When party-leaning independents are combined with those identifying with a party, Democrats lead Republicans by 45 to 42 percent.