By Anthony Salvanto, Fred Backus, Jennifer De Pinto, Sarah Dutton

Donald Trump (35 percent) continues to hold a commanding lead over the rest of the field, with a 17 point lead over his closest rival, Texas Senator Ted Cruz (18 percent). John Kasich (11 percent) has now risen to a virtual third-place tie with Marco Rubio (12 percent). Trump leads among nearly every demographic group.

More than half of Republican voters say they may still change their minds about who to support, but two thirds of Trump voters say their minds are made up.

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Seven in 10 Republican primary voters want a candidate who will shake up the system, and their top choice for the nomination is Donald Trump. Just one in four want someone who will work within the system.

Donald Trump is also seen as most likely to get things done in Washington, far outpacing his rivals on this measure.

Trump trails Cruz and Rubio on sharing the values of Republican primary voters and on having realistic policies, but half still think he is prepared to be president, and he is widely seen as the most electable candidate of the field. He rates higher than Cruz or Rubio on handling the economy and an international crisis.

Where the Race Stands

With the first votes already cast in Iowa and New Hampshire -- and with the once sprawling Republican presidential field whittled down to six remaining candidates -- Donald Trump continues to hold a double-digit lead over the rest of the Republican field nationally. Thirty-five percent of Republican primary voters support Trump, 17 points ahead of his closest rival, Texas Senator Ted Cruz (18 percent). These numbers are virtually unchanged from a month ago.

There has been little movement among the remaining six Republican candidates, with one notable exception. After a strong showing in the New Hampshire primary, Ohio Governor John Kasich -- who has consistently trailed all the remaining candidates since August -- has shot up to 11 percent, challenging Florida Senator Marco Rubio for third place. Jeb Bush (4 percent) has slipped to last place among the six remaining candidates, behind Ben Carson (6 percent).

Forty-six percent of Republican primary voters say they have now made up their minds about whom to vote for, up from 35 percent last month. But Trump's supporters are surer about their choice: Two-thirds of Trump voters now say they have made up their minds. Among those supporting other candidates, the race is more fluid; two-thirds of them may still change their minds.

Trump's support cuts across nearly every demographic group in the Republican electorate. He holds a double digit lead among Republicans and independents, men and women, white evangelicals, and Americans of all income levels. He leads among Republican voters of all age and education levels, but does particularly well among voters without college degrees.

Trump also holds a double digit lead among moderates and those who describe themselves as somewhat conservative, and has a five point lead over Ted Cruz among very conservative Republican voters.

Enthusiasm for the Eventual Nominee

Thirty-five percent of Republican primary voters would enthusiastically support a Trump candidacy (down slightly from 40 percent in January), slightly higher than enthusiasm for Ted Cruz or Marco Rubio if either of them became the Republican nominee.

Just one in five Republican primary voters would not support Donald Trump if he were to win the nomination.

Shaking Things Up, Getting Things Done

Most Republican primary voters don't want the next president to cater to the status quo in Washington. Seventy percent want someone who will shake up the political system, while just 24 percent want someone who will work within the political system.

Donald Trump is the top choice among those who want a candidate that will shake up the system, at 42 percent. Those who want a candidate who will work within the system are torn between Marco Rubio (25 percent) and John Kasich (21 percent).

And by a large margin, Trump is seen as the candidate most likely to get things done once he gets to Washington. Forty-three percent of Republican primary voters pick Trump for this, compared to 16 percent for Ted Cruz and 13 percent for Marco Rubio.

Candidate Strengths and Weaknesses

Trump is also seen as by far the most electable of the candidates still in the race -- 53 percent of GOP primary voters think that Trump has the best chance of winning in November, and confidence in Trump's chances in the general election has risen considerably over the course of the campaign. In July 2015, only 26 percent of GOP primary voters were confident Trump would win. Even those not backing Trump pick him as the candidate most likely to win in November.

As attention shifts to the Supreme Court after the death of Justice Antonin Scalia, Republican primary voters are split between Donald Trump (25 percent) and Ted Cruz (25 percent) over who is most trusted to make appointments to the Supreme Court. Moderates strongly favor Trump (27 percent), while conservatives favor Cruz, and those who consider themselves very conservative chose Cruz (38 percent) over Trump (19 percent).

Trust Most to Make Appointment to the Supreme Court

Fifty-one percent of Republican primary voters think Donald Trump is prepared to be President - though slightly more think so of Ted Cruz (57 percent). Just 42 percent of Republican primary voters think Marco Rubio is prepared to be President.

Despite his many perceived strengths with voters, the percentage who think Donald Trump shares their values has dropped slightly since January, from 59 percent last month to 50 percent today. Trump trails both Cruz and Rubio when it comes to sharing the values of Republican primary voters.

In addition, many Republican primary voters don't think Donald Trump's policies are realistic: 44 percent think they are and 50 percent think they are not. In contrast, majorities of Republican primary voters think both Ted Cruz (57 percent) and Marco Rubio (58 percent) have realistic policy proposals.

Not surprisingly, Trump voters see things differently. Nine in 10 Trump voters think he shares their values, and eight in 10 Trump voters think his policies are realistic.

Far more Republican primary voters are very confident in Donald Trump's ability to handle the economy (49 percent) than either Ted Cruz (21 percent) or Marco Rubio (17 percent), and he has a clear, if smaller, advantage over both Cruz and Rubio on handling an international crisis.

What Republicans Want in a Candidate

Overall, a candidate who shares their values (42 percent) is the candidate quality most desired by Republican primary voters. Twenty-eight percent of Republican primary voters most want a candidate who says what they believe, while experience (15 percent) and electability (12 percent) are further down on the list of priorities. For Trump voters, however, having a candidate who says what he believes (39 percent) is more important than having a candidate who shares their values (33 percent).

This poll was conducted by telephone February 12-16, 2016 among a random sample of 2,007 adults nationwide, including 1,641 registered voters and 581 registered voters likely to vote in a Republican primary. Data collection was conducted on behalf of CBS News by SSRS of Media, PA. Phone numbers were dialed from samples of both standard land-line and cell phones.

The poll employed a random digit dial methodology. For the landline sample, a respondent was randomly selected from all adults in the household. For the cell sample, interviews were conducted with the person who answered the phone.

Interviews were conducted in English and Spanish using live interviewers.

The data have been weighted to reflect U.S. Census figures on demographic variables.

The error due to sampling for results based on the entire sample could be plus or minus two percentage points. The margin of error for the sample of 581 Republican primary voters could be plus or minus five percentage points. The error for other subgroups may be higher and is available by request. The margin of error includes the effects of standard weighting procedures which enlarge sampling error slightly.