A new CBS poll shows Donald Trump opening up an 18-point lead in California, his largest of the primary campaign.

Trump currently has the support of 49 percent of likely Republican primary voters, while Sen. Ted Cruz has 31 percent. Ohio Governor John Kasich is a distant third, with 16 percent support.

The poll, conducted for CBS by YouGov from on-line voter screens, finds Trump with his largest level of support in the Golden State. Other polls, conducted at the beginning of April, showed Trump with around 40 percent support from California Republicans. Support for both Cruz and Kasich, however, has slipped slightly over the past two weeks, according to the poll.

The race in California, however, remains very fluid. Just over half of Republicans, 51 percent, say they have definitely made up their mind on whom to support. Almost one in five Republicans, 17 percent, say there is a good chance they could still change their mind.

Trump isn’t suffering from any gender gap in California. He leads men by 21 points and women by 18 points. This is very different than a recent Field poll in California, which found a significant gender gap in Trump support. In that poll, Trump led among men by 17 points while trailing women by 4 points.

He is weakest with voters under 30. He has just 39 percent support from these young voters, leading Cruz by just 5 points, while he boasts 50 percent support in all other age groups.

California Republicans would be happier with Trump as the nominee than any other candidate. Just over 60 percent say they would be “enthusiastic” or “satisfied” with Trump as the nominee, while 57 percent say the same about Cruz and just 50 percent about Kasich. Half of California’s Republicans, in fact, would be “dissatisfied” or “upset” if Kasich were the nominee.

Trump also has the clear edge on candidate traits. He has a 19 point edge over Cruz, 49-30, on who is most electable in the general. He has a 16 point edge, 46-30, on “understanding” the voters. A strong majority, 57 percent, think Trump is most “effective at getting things done” and half of Republicans see him as the most “authentic.”

The CBS poll also asked California Republicans about recent controversies surrounding the selection of delegates and the prospect of a contested convention. A slim majority, 51-49, of Republicans felt the primary process has been “fair.” A small majority, 50-44, also felt that Trump, Cruz and Kasich should battle for the nomination at the convention is a candidate is short of the 1,237 delegate threshold, rather than award the nomination to the candidate with the most delegates.

The California primary, on June 7th, is the richest delegate prize in the Republican contest. Just 13 delegates are awarded to the winner of the statewide vote, however, while a total of 159 delegates are awarded through the state’s 53 congressional districts. The winner of each district receives 3 delegates, making the California contest effectively 54 mini-primaries.

Voting in the California primary is only open to registered Republicans.

The Califorina primary is among the last states to vote on June 7th. The outcome of the primary here may well determine whether or not Donald Trump can secure the minimum number of 1,237 delegates he needs to win the nomination ahead of the RNC convention. This poll suggests he has a good chance of achieving that goal.