Yes, if your taxable income is $46,000 and you have sufficient compensation to make the IRA contribution, a $4,325 deductible traditional IRA contribution will reduce your taxable income to $41,675 where all of your long-term capital gains will be taxed at 0%.
With no IRA deduction, if $46,000 is your gross income rather than your taxable income, your taxable income is already below the $41,675 taxable-income threshold above which LTCGs get taxed at 15%.
