WASHINGTON — Donald Trump’s lead over Ted Cruz has shrunk to just 4 percentage points in the second national poll after last week’s Republican debate.

Trump wins 28% support in a Quinnipiac poll released Tuesday, with Cruz nipping at his heels with 24%. Following that pair is Marco Rubio with 12% support, Ben Carson with 10%, Chris Christie with 6% and Jeb Bush with 4%. The survey was in the field entirely after CNN’s debate in Las Vegas on Dec. 15.

Cruz has been steadily climbing and overtaking Trump in Iowa, and there is some evidence that the Texas senator is managing to perform similarly nationally. But in most polls, Trump’s national lead has stretched to new heights, with some recent surveys showing that more than 40% of Republican voters would support him today.

A Fox News poll taken similarly after the debate showed Trump with 39% support.

Quinnipiac’s national polling has consistently shown lower support for Donald Trump than other national phone polls, and that seems to be the case again in Tuesday’s survey. Their last pre-debate poll showed Trump at 27%, Rubio at 17% and Carson and Cruz both at 16%.

Despite his GOP frontrunner status, 50% of American voters nevertheless told Quinnipiac that they would be “embarrassed” to have Trump as the face of the U.S.

Among Democrats, Hillary Clinton continues to enjoy a large lead over Bernie Sanders, winning 61% of the vote to Sanders’ 30%.

And in hypothetical head-to-head matchups, Trump continues to fare poorly, with Clinton beating him by 7 points and Sanders doing so by 13 points. Other Republicans apparently pose greater threats to the GOP: Cruz and Clinton tie at 44% each, and Clinton only beats Rubio 44% to 43%.

Quinnipiac polled 508 Republicans for a margin of error of 4.4 percentage points and 462 Democrats for a margin of 4.6 percentage points.