# Enumerate align problem inside theorem

I am trying to add a separation between the beginning of a theorem environment and an enumeration. I want this:

Theorem
(1)
(2)
(3)


And not this:

Theorem (1)
(2)
(3)


I know a solution is using \leavevmode, but what I want to do is to automatically include this command inside my theorem environment, so I tried this:

\theoremstyle{definition}
\newtheorem*{demo}{Demostración:}
\AtBeginEnvironment{demo}{\leavevmode}


But this is doing nothing. I mean, it doesn't give me an error, it just does nothing (but if I include \leavevmode after the \begin{demo} it works. I think I'm loading all the necessary packages.

Hope you can help me :)

You can do this with a new environment, built around a standard theorem.

\documentclass{amsart}

\newtheorem{theorem}{Theorem}
\newenvironment{ltheorem}{\begin{theorem}\leavevmode}{\end{theorem}}

\begin{document}

\begin{ltheorem}
\begin{enumerate}
\item One
\item Two
\item Three
\end{enumerate}
\end{ltheorem}

\end{document}