WASHINGTON (AP) - The contentious debate over overhauling the health care system shifts to the Senate and a moderate Republican, Sen. Susan Collins of Maine, says the Senate will not take up the House bill and will instead start from scratch .

Some senators have already voiced displeasure with the health care bill that cleared the House last week. They cite concerns about potential higher costs for older people and those with pre-existing conditions, along with cuts to Medicaid.

President Donald Trump is urging Senate Republicans to "not let the American people down." Trump's budget director, Mick Mulvaney, also says the version that gets to the president will likely differ from the House measure. Such a scenario would force the House and Senate to work together to forge a compromise bill.

Meanwhile, a health advocacy group is launching a six-figure advertising campaign this week targeting 24 Republican House members who voted to repeal Barack Obama's health care law.

Save My Care says the campaign will include a mix of TV and digital advertising, costing more than a half million dollars.

Among those being targeted are Tom MacArthur of New Jersey, the moderate Republican who helped revive the bill by authoring an amendment on pre-existing conditions, as well as Dave Brat of Virginia, a conservative Freedom Caucus member.

The group says it will emphasize the lawmakers' support for a House bill that's estimated to reduce coverage for 24 million people over 10 years and let insurance companies charge more for older people.

The campaign will run in congressional districts in 15 states.

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