A new poll says Sen. Ted Cruz is solidifying his second-place footing over Sen. Marco Rubio, but says both candidates still trail Donald Trump by a wide margin nationally.

In the latest national NBC News/SurveyMonkey weekly online tracking poll released Tuesday, Trump leads the way with 38 percent. Texas Sen. Ted Cruz is next with 18 percent, while Rubio collected 14 percent, a decrease of 3 points from the last survey.

Ben Carson took 8 percent, John Kasich jumped 4 points to 7 percent, and former Gov. Jeb Bush had just 4 percent.

The poll said more than half of the GOP voters surveyed, 56 percent, believe Trump will be the nominee, up from 42 percent last week. Just 22 percent and 10 percent feel the same about Cruz and Rubio, respectively.

On the Democratic side, the poll suggests that Hillary Clinton's lead over Sen. Bernie Sanders is slowly being whittled away.

Among Democrats, Clinton leads Sanders 50 percent to 40 percent. But in the last survey, Clinton had 51 percent to Sanders' 39 percent. Nine percent now say they still do not know.

Clinton's largest lead was at the end of December, when she had 53 percent to Sanders' 36 percent, a gap that has consistently decreased week to week.

While the youngest demographic of voters largely support Sanders, just 25 percent of millennial black voters said they are backing the Vermont senator, compared with 64 percent who said they are supporting Clinton. The reverse is true among white millennials, who back Sanders 75-22.

The online poll of 11,400 registered voters nationwide was conducted online from Feb. 8-14 and carries an overall margin of error of plus or minus 1.1 percentage points.