âIâm taking a big risk, because if Luther doesnât make it, theyâre going to go after me,â the president said of the news media.
Mr. Trump assured the crowd that should that happen, he would intensively back Mr. Strangeâs rival, drawing an ovation from the arenaâs capacity crowd even as he essentially undercut his own message days before voters go to the polls.
âIf his opponent wins, Iâm going to be here campaigning like hell for him,â Mr. Trump said, although he added that Mr. Moore âhas a very good chance of not winningâ in the general election against a Democrat.
Mr. Trump inserted himself into the Alabama race last month, taking many Republicans by surprise with a posting on Twitter that said Mr. Strange had his âcomplete and total endorsement.â But then Mr. Trump was quiet on the matter for weeks, calling into question his willingness to throw the full weight of the presidential bully pulpit behind the Alabama senator.
Mr. Trumpâs decision to back Mr. Strange in the first place ran counter to the advice of some of the presidentâs advisers, who had privately argued that Mr. Trump should not expend precious political capital in support of a candidate who could lose. More recently, Stephen K. Bannon, his former chief strategist, has publicly urged Mr. Trump to abandon Mr. Strange, portraying him as a lieutenant of Mr. McConnell and the personification of the âswampâ of establishment Washington that the president has condemned.
Only hours before Mr. Trump was to appear in Huntsville, his own secretary of Housing and Urban Development, Ben Carson, issued a statement praising Mr. Moore as âsomeone who reflects the Judeo-Christian values that were so important to the establishment of our country.â It underscored the degree to which Mr. Trumpâs endorsement of Mr. Strange has driven a wedge between the president and his core supporters, who flocked to his anti-establishment message and many of whom are backing Mr. Moore.
Yet Mr. Trump, appearing at ease in campaign mode after a week of scripted speeches and diplomatic maneuvering at the United Nations General Assembly, thrilled Alabamians with tough talk about national security and immigration, and dismissing as a âhoaxâ the notion that Russia meddled in the 2016 election despite the unanimous consensus of the nationâs intelligence officials.
He indulged himself on several pet topics that were of no apparent help to Mr. Strange, including the presidentâs Electoral College success, his decision to work with congressional Democrats and what he argued was the growing penchant of N.F.L. referees to throw flags for hard hits.
The digressions were part of a meandering, more than hourlong speech, interspersed with scripted praise for Mr. Strange and extemporaneous declarations of wonder about the sheer size of the 6-foot-9 senator known as Big Luther.
âThat is the tallest human being Iâve ever seen,â Mr. Trump said at one point.
âLuther wants to end business as usual, stop the insider dealing, and Luther is determined to drain that swamp,â Mr. Trump said. âLuther has proved that heâs not beholden to anyone.â
Mr. Trump said Mr. Strange was the only Republican senator who did not solicit a personal favor from him when the president was working the phones earlier this year trying to persuade lawmakers to support a plan to repeal the Affordable Care Act. Lapsing into a Southern accent to imitate various Republican senators he said had begged him to visit with their families or dine with their wives as he lobbied for their votes, the president said Mr. Strange had demanded nothing, saying simply: âIf you want my vote, you have it.â
âI went home and told my wife thatâs the coolest thing thatâs happened to me in six months,â Mr. Trump said. âWe have to be loyal in life.â
Mr. Strange was plainly elated to have the president make a long-anticipated campaign appearance on his behalf â he clapped joyfully as Air Force One touched down in Huntsville as the sun set. Many in the rally crowd were clearly here to see Mr. Trump as well, and either cared little about Mr. Strangeâs candidacy.
Seemingly worried about turnout, supporters of Mr. Strange sent three emails on Thursday to Alabama Republicans urging them to come to the rally â one to Mr. Strangeâs list, another to Mr. Trumpâs list of Alabama backers and another from the stateâs most powerful business lobby.
And Mr. Strange, in a debate on Thursday with Mr. Moore, repeatedly promoted the rally, at one point even suggesting 20,000 people could show up.
Mr. Trumpâs decision to line up with Mr. Strange has thrilled business-aligned Republicans in Alabama and in Washington, offering a sheen to mask any scent of the senatorâs past as a lobbyist in the nationâs capital for much of the 1980s.
âWe have worked together to fight the establishment,â Mr. Strange told the crowd of himself and the president, calling Mr. Trump âmy friendâ and wearing his signature âMake America Great Againâ hat. He said the raceâs outcome âwill determine whether the president has the votes he needs in the Senate to stand up to Mitch McConnell, John McCain.â
âHe knows Iâve got his back,â Mr. Strange said of the president.
Mr. Mooreâs anti-establishment backers argue that the president is being hoodwinked, and that a victory by Mr. Strange would amount to a rejection of Trumpism.
âGuys, the swamp, itâs trying to hijack this presidency,â former Gov. Sarah Palin of Alaska told Moore supporters at a rally in Montgomery, the state capital, on Thursday night. âThe swamp is trying to steal the victory that we worked so long and hard for.â
The bitterness even came through in the invocation at the Thursday gathering, when state Supreme Court Justice Tom Parker used the prayer to scorn Mr. Strange for hiding âbehind the skirts of others.â
The president is beloved by Alabama conservatives â polls show his approval ratings well into the 80 percent among the stateâs Republicans â but his decision to aggressively intervene in the race only four days before the runoff has perplexed some of his admirers. Some of the most hard-line Republicans who are backing Mr. Moore are also the same voters who flocked to the presidentâs candidacy last year.
âHis supporters are Moore people, itâs overlapping,â said Steve Flowers, a former Alabama Republican legislator-turned-political columnist. âAnd theyâre not going to change because Trump asked them to. Theyâve known Moore a long time.â