President Donald Trump’s support among the Senate Republican Conference may be eroding as he attempts to solidify his control over a specific power the Constitution exclusively grants to Congress.The New York Times reported Thursday that Sen. Susan Collins (R-Maine), who chairs the Senate Appropriations Committee, is now siding with her Democratic colleagues as Trump attempts to wrest control of spending authority. Collins co-signed a letter to Trump with ranking member Sen. Patty Murray (D-Wash.) protesting Trump’s refusal to disburse $2.9 billion in funding already approved by Congress.Collins took issue with Trump not freeing up $750 million in international disaster assistance, $750 million in migration and refugee assistance, $234 million for the National Science Foundation, $100 million for the National Oceanic and Atmospheric Administration and $115 million for international narcotics control and enforcement, among other funds not disbursed. That money was part of the six-month continuing resolution (CR) that Congress passed earlier this month in order to keep government agencies funded through the end of the current fiscal year.READ MORE: ‘It’s just that simple’: Rubio admits to jailing immigrants for their political views”Just as the president does not have a line-item veto, he does not have the ability to pick and choose which emergency spending to designate,” Collins’ and Murray’s letter read. “It is incumbent on all of us to follow the law as written — not as we would like it to be.”Collins particularly took issue with Trump withholding the money for drug enforcement, telling the Times that the U.S. “need[s] the help of other nations to stop that.””Why would you want to do that, given the huge drug problem that we have had?” said the Maine Republican.Trump not disbursing funds appropriated by Congress is not only a violation of federal law, but also of the Constitution. The Impoundment Control Act of 1974 (passed during former President Richard Nixon’s tenure) explicitly prevents presidents from not disbursing money that Congress has included in spending bills. And Article I, Section 8 of the U.S. Constitution states that Congress alone has the power to “lay and collect Taxes, Duties, Imposts and Excises, to pay the Debts and provide for the common Defence and general Welfare of the United States.” READ MORE: ‘Different day’: GOP lawmakers ‘OK with’ Trump plan to ‘impound’ money from CongressIn a recent Senate floor speech, Murray tore into the Trump administration for ignoring Congress’ authority under the Constitution to set spending levels for federal agencies.”Right now we have a couple of billionaires running our country straight into the ground who seem to have skipped American history because President Trump and Elon Musk don’t seem to care much about our Constitution,” she said. “Their lack of interest in that section of the Constitution doesn’t make it any less real at all.”Fox News reported that when Republican leaders were whipping votes for the CR several weeks ago, several hardline fiscal hawks among the House Republican Conference signaled that they would support the legislation with the understanding that Trump would later “impound” money for agencies and programs he didn’t approve of.Click here to read the Times’ report in its entirety (subscription required). READ MORE: ‘Freaking out’: Trump mocked for saying ‘out loud’ why he withdrew Stefanik’s nomination