将等号与和对齐

Question

考虑以下示例：`

        \documentclass[bibliography=totoc,toc=sectionentrywithdots,DIV=10, parskip=half, 12pt, captions=tableheading]{scrartcl}     
     \usepackage{amsthm,amsmath,amssymb}
\begin{align*}  
       \begin{split}
         &\mathbb{P}() \\ &=\mathbb{P}()\\ &= \sum\limits_{k=0}^{j} \mathbb{P}()
       \end{split}
\end{align*}`

如何才能使总和前​​面的等号与概率前面的等号完全一致？