Is the War Powers Act of 1973 unconstitutional for Democratic presidents and valid for Republicans?

In 1973 The 93 rd Congress of the United States was Democratic. Both houses had a comfortable majority but not a super majority in either house Democratic. That Congress passed the War Powers Act. This was a designed to limit the power of the president to use American military on foreign countries (Viet Nam) President Nixon vetoed the bill. A bi-partisan vote passed the act over the presidents veto. There was never any question about the law when Republicans were president and they followed it. Democrats have now deemed it unconstitutional with a Democratic CiC. Will it suddenly become the law of the land and Constitutional when there is a Republican in office?