The Senate is on track to start procedural votes on Wednesday, Texas Senator John Cornyn, the Republican whip, told reporters in Colorado at a donor summit for the Koch political network. Passing the bill won’t get any easier by delaying it, he said.

“If people want to get to ‘yes,’ then you can have good-faith negotiation and get them there. But it’s going to be close,” said Cornyn.

Related: Four GOP senators spurn health plan aimed at unifying party

Collins said she’s “very concerned” about cuts in coverage for older people with serious, chronic illnesses and the impact on lower-income Americans, as well as the cuts in funding for rural hospitals and nursing homes through Medicaid reductions.

Medicaid concerns

“Based on what I’ve seen, given the inflation rate that would be applied in the outer years to the Medicaid program, the Senate bill is going to have more impact on the Medicaid program than even the House bill,” she said. Seven or eight Republican senators have been meeting under the leadership of Rob Portman of Ohio to express concern about Medicaid, Collins added.

Related: Two studies look at Medicaid expansion pros, cons

Also on ABC, Kellyanne Conway, an adviser to President Donald Trump, said the reduction in Medicaid funding wasn’t a “cut” but an assumption of a slower rate of growth in future.

Only a few hours after the bill was released, four conservative Senators led by Rand Paul of Kentucky announced that they’ll need a host of changes to get to “yes.” On Friday, Dean Heller of Nevada added his name to the dissenters, saying the plan would take away insurance from too many people in his state.

Heller, who’s up for re-election in 2018, stood with his state’s Republican governor, Brian Sandoval, in announcing his opposition. On Sunday, Governor John Kasich of Ohio, another Republican, also opposed the measure. “I don’t think the bill is adequate,” Kasich said on CNN’s “State of the Union.”

‘Promised too much’

Paul said on ABC that the Republicans “promised too much” and that “there’s no way the Republican bill brings down premiums.” He said if McConnell can’t get the required votes to pass the bill, he could support an effort that focuses on repealing Obamacare.

Related: How killing Obamacare might save some of Obamacare, for a while

McConnell can only afford to lose two Republican votes amid unanimous Democratic opposition to the health-care bill. Moderates including Collins and Lisa Murkowski of Alaska are also concerned about cuts to funding for Planned Parenthood, the women’s health clinics. Collins said she is “optimistic we’ll prevail on that issue.” Murkowski said in a statement on Thursday that she will “crunch the numbers.”

McConnell has said he wants the chamber to vote on the measure next week, after an open-amendment process. Lawmakers leave town the following week for an Independence Day recess, but even some Republicans are urging him to slow down.

Senator Ron Johnson of Wisconsin, part of the faction that thinks the bill doesn’t go far enough in rolling back Obamacare, said he’d like to delay a vote.

‘Let’s not rush’

“Let’s not rush this process,” Johnson said on NBC’s “Meet the Press.” “Let’s have the integrity to show the American people what it is.’’

Related: Sanders signals backing of Senate slowdown over health care bill

On the other end of the ideological spectrum, Senator Bernie Sanders, the Vermont independent, said on NBC that “there’s no way on God’s Earth that this bill should be passed this week.” Sanders, who in the past has criticized Obamacare as insufficient, said he’ll push ahead with legislation for a “Medicare for all, single-payer program.”

Chuck Schumer, the Senate Democratic leader, said the Republican bill has “at best a 50-50 chance” of passing in its current form. ‘The bill is just devastating. And that’s what’s making it so hard for them to pass it,” Schumer said on ABC.

Trump jawboning

The views of Senate’s conservative anti-Obamacare faction were echoed on Saturday by leaders of the influential Koch network during the donor retreat in Colorado.

“We’ve been disappointed that movement has not been more dramatic toward a full repeal or a broader rollback of this law, Obamacare,” Tim Phillips, president of Americans for Prosperity, funded by billionaire brothers Charles and David Koch, told reporters.

The CBO is expected to release its estimate of the bill’s impact in the next few days. That’s being watched to see how it compares with the House bill, passed in May, which the non-partisan office estimated would cause some 23 million Americans to lose health insurance during the next decade.

Trump on Saturday started to pressure the potential Republican holdouts. “I cannot imagine that these very fine Republican Senators would allow the American people to suffer a broken ObamaCare any longer!” Trump said on Twitter.

Conway said the president has been working the phones and having personal meetings with lawmakers to help pass the bill. Still, in an interview with “Fox and Friends” broadcast early Sunday, Trump admitted for the first time that he’d called the House health bill “mean,” despite marking its passage in that chamber with a jubilant ceremony in the White House Rose Garden.

‘Sense of urgency’

Cornyn said of Trump’s activities that “he’s going to be important in the process” while adding, “we’re trying to hold him back a little bit. There’s a sense of urgency to move ahead because insurance companies are pulling out of health-care exchanges, Cornyn said, adding that he thinks “about Aug. 1st” is the deadline for acting.

Even with opposition within his own party, McConnell may have some tricks up his sleeve. The veteran Senate tactician may have made some intentional omissions in the “discussion draft” he released on June 22 so that other lawmakers can be seen to secure public victories in return for their support.

In that vein, Senator Bill Cassidy of Louisiana said Sunday on CBS’s “Face the Nation” that while he’s undecided on the bill, he’s open to a “yes” vote if certain elements that affect his state can be addressed. “I frankly would like more days to consider this,” he said.

Copyright 2018 Bloomberg. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.